The capability to rapidly conduct biochemical and other assays is critical in a wide variety of fields. For example, rapid and accurate diagnosis of infectious disease is crucial both for the effective management of disease in individual subjects and for ameliorating the public health problems of multi-drug resistant pathogens and community acquired infections.
Current PCR-based DNA amplification methods suffer from a number of drawbacks including high reagent costs, labor intensity and susceptibility to cross-contamination. Furthermore, compared to culture, PCR tests are less capable of simultaneously assaying multiple species, virulence factors, and drug resistant markers. They often lack sensitivity and cost-effective quantification of the pathogen. There is a need in the art for improved devices for nucleic acid detection that would overcome these limitations while also miniaturizing and automating the technique so that these assays could potentially be applied at the point-of-sample collection with minimal training.
Nucleic acid sequencing is becoming increasingly common in a variety of fields, such as whole genome sequencing, diagnostics, pharmacogenomics, and forensics. However, the sequencing field has been hampered by the expensive nature of sequencing machines. The development of inexpensive, high-throughput testing systems is critically important to the spread of genetic testing and the many advantages that are associated with it. There is thus a need for new technological platforms that allow one to quickly and reliably sequence nucleic acids at a reasonable cost. The invention described herein provides an inexpensive, droplet-based sequencing system.
Immunoassays are widely used for clinical diagnostics and constitute more than a $3 billion market in the U.S. alone. Immunoassays are among the most sensitive and specific methods that are routinely used in a clinical laboratory. Immunoassays make use of the high-affinity and specificity in binding between an antigen and its homologous antibody to detect and quantify the antigen in a sample matrix. Heterogeneous immunoassays such as ELISA (Enzyme-Linked Immunosorbent Assay) are among the most sensitive and specific clinical analysis methods, and have been widely used for identification of a large class of antigens and antibodies. For example, immunoassays are performed, among other things, for identification of cardiac markers, tumor markers, drugs, hormones, and infectious diseases.
Small sample consumption, faster analysis, and complete automation are three highly desirable features that require continual improvement in any clinical analyzer. Although state-of-the-art laboratory immunoassay analyzers offer good automation and throughput, they require a significant amount of sample per test (including dead volumes) and lengthy analysis times. The long assay times and the large size of these analyzers make them impractical for use in a point-of-sample collection setting.
Also, there is considerable variability in the immunoassay performance, in large part attributed to the techniques being operator dependent, resulting in difficulty comparing results from study to study and even within the same study if more than one laboratory is used. A fully automated and integrated analyzer that eliminates the operator dependence and standardizes results for the immune monitoring assays would considerably improve the interpretation of results from assays.
Though significant advances have been made in the automation of immunoassays, these analyzers are prohibitively expensive and are not affordable in a low-throughput research setting. Lower end systems with automated plate washers, incubators and integrated optics still require a skilled technician to perform several key steps in an immunoassay such as preparing microtiter plates with antibodies and loading samples onto the plates. This results in human error due to repeated manual intervention and is a major source of inter-assay and intra-assay variation.
There is also a need for point of sample collection testing in a variety of fields, such as medicine, environmental, and bioterrorism-related detection fields. As an example, point-of-sample collection (POC) testing for bedside blood analysis has improved but remains a key challenge for modern medical care. Ideally, POC testing would enable the clinicians to diagnose and implement life-saving technologies in real-time by avoiding the need for large laboratory facilities. There remains a need in the art for a lab-on-a-chip that enables simultaneous monitoring of blood gases, metabolites, electrolytes, enzymes, DNA, proteins, and cells, on low sample volumes at the POC.
Microfluidic control of the fluids is an essential requirement for a successful lab-on-a-chip. Microfluidic systems can be broadly grouped into continuous-flow and discrete-flow based architectures. As the name suggests, continuous-flow systems rely on continuous flow of liquids in channels whereas discrete-flow systems utilize droplets of liquid either within channels or in a channel-less architecture. A common limitation of continuous flow systems is that liquid transport is physically confined to permanently fixed channels. The transport mechanisms used are usually pressure-driven by external pumps or electrokinetically-driven by high-voltages. These approaches involve complex channeling and require large supporting systems in the form of external valves or power supplies. These restrictions make it difficult to achieve a high degree of functional-integration and control in conventional continuous-flow systems, particularly in realizing a handheld device at the point-of-sample collection. There remains a need in the art for a point of sample collection testing system that makes use of droplet manipulations and especially a system that can accomplish multiple tests or multiple types of tests on a single chip.